The season opens with a three-episode flashback adapted from the light novel Dazai, Chuuya, Fifteen Years Old .

The third season of Bungo Stray Dogs is split into two primary narratives: an introductory flashback arc focusing on the past of Dazai and Chuuya, followed by the high-stakes "Cannibalism" arc in the present day. The Prequel: Dazai and Chuuya (Ages 15)

After defeating the mastermind Arthur Rimbaud, Chuuya is betrayed by his own group and eventually joins the Port Mafia at Dazai's invitation. The Present: The Cannibalism Arc